A. Regular Expressions
A regular expression defines a set of one or more strings of characters. A simple string of characters is a regular expression that defines one string of characters: itself. A more complex regular expression uses letters, numbers, and special characters to define many different strings of characters. A regular expression is said to match any string it defines.
This appendix describes the regular expressions used by ed, vim, emacs, grep, awk/mawk/gawk, sed, Perl, and many other utilities. Refer to page 517 for more information on Perl regular expressions. The regular ...
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